Compositions for cleaning hard surfaces, including compositions for removing limescale, are well known in the art. Such compositions, which are characterized mainly by a strong acidity, are disclosed for instance in EP 496 188.
Limescale is mainly found in such places as sinks, toilet bowls and bathtubs, i.e. vertical surfaces. Therefore, it is desirable to give some viscosity to compositions for removing limescale so as to prevent said compositions from running down said vertical surfaces. Indeed thick compositions cling to vertical surfaces, thus they have more time to act on vertical surfaces before they run down said surfaces. It is however undesirable to use thickener compounds in such compositions for various reasons. For instance, thickener compounds may significantly raise formula costs. Also, thickeners may create issues relating to processing and product stability, especially in extreme acidic conditions. Furthermore, thickeners may affect the limescale removing performance of the composition. Finally, thickeners do not contribute to the cleaning performance of the composition.
It is therefore desirable to provide limescale removing compositions in the form of self-thickened systems. Self-thickened systems have been disclosed for instance in co-pending EP 92201412.1. In these systems, the thickening effect is obtained by the combination of an anionic surfactant, a nonionic surfactant and an electrolyte. It has however been found that such systems are not optimum for limescale removing compositions. Indeed, this approach does not seem to provide viscosity in a strongly acidic system unless very high levels of ingredients are used, and strong negatives have been observed on limescale removal. Furthermore, the stability of anionic surfactants may be problematic in such strongly acidic conditions.
It has now been found that a stable self-thickened effect could be obtained in an acidic medium, without compromising on the limescale removing efficiency of the composition by combining a quaternary ammonium salt surfactant with a nonionic surfactant. This solution has the additional advantage that the thickening system also fulfills a detergent function.
Additionally it has been found that the compositions according to the present invention have the advantage that the use of the quaternary ammonium salts cationic surfactants described hereinafter in combination with an acid provides significant disinfectancy benefits. This advantage is particularly useful in a composition which is meant to be used primarily on bathroom and kitchen surfaces.
GB 2 071 688 teaches that quaternary ammonium salts can be used to thicken an acidic solution, provided they are combined with an amine or amine oxide. In the '688 patent, nonionic surfactants are presented as an alternative to the quaternary ammonium salts.
EP 188 205 teaches that quaternary ammonium salts can be used to thicken an acidic solution, provided they are combined with a strong mineral acid.